This invention relates to a heat exchanger.
The type of heat exchanger here under consideration is one in which there is a plurality of tubes through which, in use, a first medium flows to accept heat from, or transfer heat to, a second medium flowing around and between the tubes. In such heat exchangers, one of the media is usually constrained to follow a tortuous path, so increasing its residence time in the heat exchanger and increasing the amount of heat which is transferred from one medium to the other.
Typical examples of prior art heat exchangers are seen in U.S. Pat. Nos. 2,391,244 (Jackson), 2,502,675 (Simpelaar), 2,48,145 (Tinker) and 3,351,131 (Berthold). In each of these patents, a series of spaced baffles span partially and transversely across the interior of the heat exchanger housing, and define the tortuous route which that medium flowing around the tubes is obliged to follow. In each case, the tubes of heat exchanger pass through the baffles. It is common for the baffles to be fixed permanently to the tubes, with the result that the baffles and tubes form an integral construction (see, for instance, the U.S. patents to Jackson, Simpelaar and Tinker mentioned above). In some cases, the tube fins, which are provided to increase the heat transfer area, serve the function of baffles (see, for example, the fins 16" in the Jackson patent). Sometimes also, the baffles are secured to the wall of the heat exchanger housing or shell.
A problem with the conventional fixed baffle heat exchangers is their lack of versatility. Heat exchangers are optimally designed for one application only in accordance with the flow parameters and heat exchange requirements expected in that applicaton. Where the heat exchanger designed for one application is used in another application in which the flow rate of the medium to be cooled is greater than the design flow rate, there is usually an unacceptable pressure drop in the system. If, on the other hand, the heat exchanger is used in an application in which the flow rate is less than the design flow rate, there is inefficient heat transfer to the cooling medium.
Heat exchangers with fixed baffle arrangements lack versatility in that it is not possible to cater for different flow parameters and heat exchange requirements by withdrawing the baffles and replacing them with a different baffle arrangement or adjusting the baffles. In fact, because the tubes pass through, and are often secured to, the baffles, it is not possible to withdraw the baffles without taking apart the whole tube assembly.
It is, however, not always economically feasible to design a heat exchanger specifically for the application in which it will be used, especially in the case of low capacity heat exchangers. As a result, the tendency is for consumers to use mass-produced heat exchangers in a variety of applications for which the heat exchangers are not specifically designed, resigning themselves to the attendant loss of efficiency.
It would obviously be desirable to have a heat exchanger which has greater versatility, and the present invention seeks to provide such a heat exchanger.